A recently published report on one of the largest surveys conducted to date about seafood fraud revealed that one third of seafood species purchased at restaurants and grocery stores in cities across the United States were mislabeled. The study was conducted by Oceana, a non-profit international advocacy group, over a period of 2 years from 2010-2012, whereby over 1200 samples were collected from 674 retail outlets in 21 US states (K. Warner, W. Timme, B. Lowell, and M. Hirshfield, “Oceana Study Reveals Seafood Fraud Nationwide”, February 2013 report). DNA testing was performed on fish samples to correctly identify the fish species and uncover mislabeling. Similar conclusions could be drawn from a previous US Congressional Research Service Report regarding combating fraud and deception in seafood marketing (Congressional Research Service Report for Congress, 7-5700, www.crs.gov, RL-34124 (2010)).
Substitution of a more expensive fish by a lower-cost species is illegal. It is motivated by monetary gains by perpetrators leading to negative economic, health, and environmental consequences. Consumers and honest seafood suppliers are cheated into paying higher prices for lower-cost, less-desirable substitutes. One of most commonly substituted and more expensive fish is red snapper often swapped for tilapia. Furthermore, some fish substitutes pose health hazards. For example, the above Oceana study has determined that over 90% of what is advertised as white tuna was actually escolar, which is a snake mackerel species containing toxins known to cause gastrointestinal problems. Lastly, some substituted fish may be of an overfished or threatened species. One such fish is the Atlantic cod, which was found to be swapped for Pacific cod in the same study.
The supply chain “from boat to plate” is complex and unregulated, making such illegal activities difficult to track. Combating fish fraud requires traceability of fish supply across the entire supply chain, as well as and increased inspection. DNA testing for inspection is time consuming and can only be done on a sampling basis. The DNA testing requires taking samples of fish to a lab and waiting for results,—a process that can take days.
Wong in U.S. Pat. No. 5,539,207 discloses a method of identifying human or animal tissue by Fourier Transform Infrared (FT-IR) spectroscopy. A mid-infrared spectrum of a tissue in question is measured and compared to a library of infrared spectra of known tissues, to find a closest match. Either a visual comparison, or a pattern recognition algorithm can be used to match the infrared spectra. In this way, various tissues, and even normal or malignant (e.g. cancerous) tissues can be identified.
Detrimentally, the method of Wong is difficult to use for the purpose of seafood identification in field conditions. An FT-IR spectrometer is a complex and bulky optical device. Its core module, a scanning Michelson interferometer, uses a precisely movable large optical mirror to perform a wavelength scan. To stabilize the mirror, a heavy optical bench is used. Due to many precision optical and mechanical components, an FT-IR spectrometer requires laboratory conditions, and needs to be re-calibrated and re-aligned frequently by trained personnel. The use of an FT-IR spectrometer is dictated by the fact that the fundamental vibrational frequencies of the infrared fingerprint are present in the 2.5 to 5 micrometers region of the electromagnetic spectrum. These vibrational bands are of high resolution and high absorption levels, showing strong absorption with narrow spectral bands.
Monro in U.S. Pat. No. 7,750,299 discloses a system for active biometric spectroscopy, in which a DNA film of a particular biological subject is irradiated by a frequency-tunable millimeter-wave radio transmitter, and radio waves transmitted and scattered by the DNA film are detected. Monro teaches that radio wave scattering spectra of different DNA films are different. Therefore, transmitted or scattered radio wave spectrum can detect different DNA films, which can be associated with different fish species. In this way, species of a fish sample can be identified.
Detrimentally, the method of Monro cannot be applied to the fish samples themselves, because the signal from non-DNA tissues will overwhelm the DNA signal. Because of this, DNA of the fish samples have to be extracted and formed into a film. The sample preparation is time-consuming, and can only be done in lab conditions.
Cole et al. in U.S. Pat. No. 7,728,296 disclose an apparatus and method for detection of explosive materials using terahertz (THz) radiation. THz radiation occupies a frequency band between infrared and millimeter radio waves. Many explosive materials have a unique spectral signature in THz frequency domain, thus affording a non-invasive, remote detection of explosives with a high sensitivity. Detrimentally, THz radiation sources are bulky and expensive, limiting their current use to security-critical applications such as at airport security checkpoints.
The methods and devices of the prior art appear unsuitable for a goal of identification of seafood species in field conditions. A method and system are required that would enable a food and drug administration (FDA) official perform a quick on-the-spot seafood species identification and characterization, assisting the official in deciding whether to take a law enforcement action. Private persons, such as restaurant chefs, sushi bar patrons, and fish market customers, would also benefit from a possibility to quickly verify seafood species being purchased.